This invention relates in general to vehicle wheels and in particular to a process for fabricating a two piece vehicle wheel which includes forming a wheel disc upon the outboard end of a partial wheel rim.
It is known in the art to fabricate a two piece vehicle wheel by attaching a wheel disc to a separately formed wheel rim. Typically, the wheel disc is cast or forged while the rim is rolled or spun from strip stock. Such two piece wheels are less expensive to manufacture than a cast one piece wheel while permitting use of stylistic designs for the wheel disc.. Both the wheel disc and rim can be formed from alloys of the same light weight metal, such as aluminum, magnesium or titanium, or, as a further cost reduction, a wheel disc formed from an alloy of a light weight metal can be attached to a rim rolled from steel. When different metals are used to form the wheel disc and wheel rim, the wheel is commonly called a bimetal wheel.
To further improve the appearance of the wheel, the wheel disc can be formed to include the outboard tire bead retaining flange. The resulting wheel disc, which is called a full face wheel disc, is attached to the outboard end of a partial wheel rim. The attachment can occur at the outboard tire bead seat, the deepwell, or another location. The assembled wheel is often referred to as a full face wheel. When a tire is mounted upon a full face wheel, the joint between the wheel disc and wheel rim is completely hidden and only the wheel disc is visible. A decorative finish is often applied to the face of the wheel disc to further enhance the appearance of the wheel. Examples of typical decorative finishes include metal plating, such as chromium plating, paint and clear coatings.
Referring now to the drawings, there is shown in FIG. 1 a fragmentary sectional view of a typical prior art full face wheel 10. The wheel includes a full face wheel disc 11 formed from a light weight metal or light weight metal alloy by a conventional process, such as gravity, low pressure or die casting, or forging. The full face wheel disc 11 includes a wheel hub 12 having a central pilot hole 13 and a plurality of wheel lug holes 14 (one shown) formed therethrough. The hub 12 is supported by a plurality of wheel spokes 15 (one shown) within an annular sidewall 16. An outboard tire bead retaining flange 17 extends in a radial outward direction from the sidewall 16. An outboard tire bead seat 18 is formed in the sidewall 16 adjacent to the retaining flange 17. The sidewall 16 further includes an outboard tire safety bead 19 formed between the tire bead seat 18 and a cylindrical collar 20 which forms a portion of a deepwell 21. The collar 20 extends axially from the inboard surface of the sidewall 16.
A conventional partial wheel rim 23 is attached to the inboard side of the wheel disc 11. The wheel rim 23 can be formed from a strip of light weight metal or steel with conventional rim roll forming machinery. The wheel rim 23 includes a cylindrical outboard end 24 which forms a portion of the deepwell 21. A leg portion 24 extends axially from the drop well 21 to an inboard tire safety bead 26. An inboard tire bead seat 27 is formed adjacent to the safety bead 26. The inboard end of the wheel rim 24 terminates in a conventional inboard tire bead retaining flange 28.
An air-tight continuous circumferential weld 29 is formed between the outboard end of the wheel rim 24 and the wheel disc collar 20. The weld 29 shown in FIG. 1 is formed by a conventional electron beam or arc welding process. Alternately, a conventional friction or inertial welding process can be used to form the weld 29. During the friction welding process, the wheel disc 11 is held stationary while the wheel rim 23 is rotated with the outboard rim end 24 pressed against the wheel disc collar 20 The heat generated by friction partially melts the outboard wheel rim end 24 and the adjacent portion of the collar 20 to form the weld 29. For a bimetal wheel, a ring-shaped weld anchor (not shown) formed from a ferrous material, such as steel, can be partially embedded in the wheel disc sidewall 16. A portion of the weld anchor is exposed to form a welding surface.
Referring now to FIG. 2, there is shown a flow chart for a known manufacturing process for fabricating the full face wheel illustrated in FIG. 1. In functional block 30 a full face wheel disc is formed by a conventional process, such as casting or forging. The wheel disc is heat treated in functional block 31 and then machined to final shape in functional block 32.
While the wheel disc is being formed, a flat strip of metal is rolled into a circular hoop and the ends butt welded together in functional block 35. The hoop is formed into a partial wheel rim in functional block 36 by a conventional process, such as rolling or spinning.
In functional block 37, the partial wheel rim is attached to the wheel disc formed in functional blocks 30 through 32 by a conventional welding process. The wheel rim is usually welded to the wheel disc. Typically, it is difficult to weld the hoop coaxially with the wheel disc axis so that the inboard and outboard tire bead seats are concentric to one another. If the outboard and inboard tire bead seats of the assembled wheel are outside the required tolerance limits for concentricity, undesirable vibrations may occur when the wheel is mounted upon a vehicle and the vehicle operated. Accordingly, the tire bead seats of the assembled wheel are machined in functional block 38 to assure that the required amount of concentricity is achieved.
This invention relates to an improved process for fabricating a two piece vehicle wheel which includes forming a wheel disc upon the outboard end of a partial wheel rim.
As described above, a two piece vehicle wheel is typically fabricated by welding a preformed wheel rim to a finished wheel disc. It is usually difficult to weld the rim concentrically onto the disc. Accordingly, it would be desirable if a two piece wheel could be fabricated without welding. It would also be desirable to eliminate the weld between the wheel rim and wheel disc to simplify the manufacturing process while reducing costs.
The present invention contemplates a process for fabricating a vehicle wheel which includes an annular hoop of metal. The metal hoop is then in a wheel disc mold and a wheel disc is cast on the end thereof. The wheel disc casting and metal hoop are removed from the wheel disc mold and finished to form a vehicle wheel. The finishing can include forming the metal hoop into a wheel rim and machining the wheel disc casting. The metal hoop can be either cylindrical or flared.
The invention further contemplates that wheel disc mold defines a mold cavity and further that the mold can includes at least one optional supplemental heating element. During the casting operation, the supplemental heating element supplies additional heat to the mold cavity. Additionally, either the mold or the hoop can be optionally vibrated during the casting operation.
Alternately, the metal hoop can be mounted in die set for forging a wheel disc. A heated metal billet is placed into the die set and the die set closed to forge a wheel disc upon an end of the metal hoop. The hoop and wheel disc are then removed from the die set and the hoop formed into a wheel rim.
The invention also contemplates casting or forging a wheel disc upon the outboard end of a partial wheel rim.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.